Tellurium is a rare, semi-metallic element that is used primarily in alloys due to its ability to improve strength, ductility, and machinability. It is also used in photovoltaics, as a thermoelectric material, and in various electronic applications. Some of its compounds are also used in industrial and medical applications. However, tellurium poses environmental and health risks due to its toxicity, and its availability and production are highly dependent on other metal mining and refining processes.